Mermaid Man and Barnacle Boy / Pickles - S1-E6
Other mistake: In the end credits for the episode "Pickles", Bubble Bass is named "BubbleBass" (without a space).
MuscleBob BuffPants / Squidward, the Unfriendly Ghost - S1-E11
Other mistake: When Squidward is on the royal bed, Spongebob's Pineapple is nowhere in sight.
Culture Shock / F.U.N. - S1-E10
Continuity mistake: In "F.U.N.", Mr. Krabs sets down the Krabby Patty in front of Plankton. Almost the whole plate is on the yellow part of the table, but when the camera cuts to Plankton, the plate is mostly in the red part of the table. In the next shot, the plate returns to its original position.
Fools in April / Neptune's Spatula - S1-E19
Continuity mistake: In "Fools in April", Spongebob is scrubbing the floor and a customer comes up to him to ask for a couple of ice cubes. In the next shot, the water puddle on the floor gets increasingly bigger.
Chosen answer: You need to provide a little bit more information to be able to answer a question like this. In what region is it not being shown? I see it being replayed here in Australia fairly frequently. As for a general reason, there does not appear to be any for why it specifically might have been taken off the air in any country or region. Like any show certain episodes can sometimes not be replayed for long periods for unknown reasons.
Lummie ★